This invention relates to a V belt type of automatic transmission system and more particularly to an improved combination engine and transmission.
The use of V belt type automatic transmissions are well known. Such transmissions employ driving and driven pulleys that are interconnected by means of a belt and wherein the effective diameter of one of the pulleys is changed, normally by a centrifugal type mechanism, so as to vary the transmission ratio between the shafts. Frequently, the driving pulley is affixed directly to the engine output shaft. Although this appears to have advantages, there are a number of disadvantages to such an arrangement. In the first instance, the load caused by the tension of the belt will put a torsional or bending load on the engine output shaft. Accordingly, the bearing construction for the engine must be stronger than when the engine drives a gear type transmission. As a result, the overall engine construction becomes larger and the engine must be specifically designed for use with the transmission.
In addition, because the transmission is coupled directly to the crankshaft, the transmission will receive the torsional and vibrational loads from the engine crankshaft caused by the pulsations in the transmission of power to it. As a result, the transmission itself must be made larger so as to accommodate the loads. Such direct drives of the transmission directly from the engine output shaft increase both the engine and transmission size.
Adding to the aforenoted defects, the speed at which a belt type transmission can be driven is somewhat restricted. This is due in part to the heat generated by such transmissions. Of course, it is well known that the efficiency of an engine can be improved and its power output can be increased if the engine is driven at a higher speed. Thus, when the transmission is directly coupled to the engine, its maximum rotational speed is limited by the transmission and, accordingly, the engine may not be as efficient as possible.
It is, therefore, a principal object of this invention to provide an improved engine transmission combination.
It is a further object of this invention to provide an arrangement wherein both the engine and transmission may be lighter than previous type arrangements employing belt type variable speed transmissions.
It is a further object of this invention to provide an improved internal combustion engine and belt type variable transmission combination.
Transmissions of the type aforedescribed are frequently used in powering vehicles such as snowmobiles . . . Because of the need for maintaining lightweight and high performance for snowmobiles, the aforenoted defects have resulted in snowmobiles that tend to be heavier than desired and also which may not have the desired performance.
It is, therefore, a still further object of this invention to provide an improved, lightweight and high performance snowmobile.